Exposure of Applicators to Monosodium Methanearsonate and

8 Exposure of Applicators to Monosodium Methanearsonate and Cacodylie A c i d in Forestry

Downloaded by UNIV OF BATH on September 2, 2017 | http://pubs.acs.org Publication Date: February 25, 1985 | doi: 10.1021/bk-1985-0273.ch008

L. A. NORRIS Department of Forest Science, Oregon State University, Corvallis, OR 97331 Effective worker training and supervision and use of protective gear should minimize exposure of both humans and other animals to MSMA and cacodylic acid, herbicides used in forestry. Arsenic (As) concentration in urine, a useful index to exposure, increased rapidly with an applicator's first exposure, then decreased rapidly when exposure ceased; As concentration reflected the degree of applicator exposure and paralleled levels in small mammals in treated areas. Poor handling and application techniques raised As concentrations in urine as high as 1.8 ppm, corresponding to an exposure of at least 0.036 mg As/kg body weight/day. Proper handling techniques and use of protective gear can reduce exposure to < 0.003 to 0.007 mg As/kg body weight/day, if urine is assumed the sole excretory source. The organic arsenic-containing herbicides cacodylic acid ( d i m e t h y l a r s i n i c a c i d ) and MSMA (monosodium methanearsonate) a r e used to k i l l s e l e c t e d t r e e s ( u s u a l l y c o n i f e r s ) d u r i n g precommercial t h i n n i n g i n P a c i f i c Northwest f o r e s t s . A l t h o u g h f e l l i n g unwanted t r e e s w i t h saws i s an a l t e r n a t i v e to c h e m i c a l t h i n n i n g , i t i s c o s t l y , dangerous to f o r e s t w o r k e r s , i n c r e a s e s f i r e danger because f e l l i n g c o n c e n t r a t e s s l a s h on t h e g r o u n d , reduces a c c e s s o f domestic and w i l d a n i m a l s to f o r a g e , and has an u n s i g h t l y a p p e a r a n c e . C h e m i c a l l y k i l l e d t r e e s a r e l e f t s t a n d i n g ; the n e e d l e s o r l e a v e s f a l l f i r s t , then the b r a n c h e s , and e v e n t u a l l y the main stem. Both c a c o d y l i c a c i d and MSMA a r e r e g i s t e r e d f o r t h i s use and a r e b e i n g a p p l i e d by both p r i v a t e and p u b l i c forest-management groups i n t h e P a c i f i c Northwest and elsewhere i n t h e U n i t e d S t a t e s . T o t a l use f i g u r e s a r e d i f f i c u l t to c o m p i l e , t h e l e v e l v a r y i n g o v e r t i m e ; f o r example, the USDA F o r e s t S e r v i c e a p p l i e d 18,000 l b on 3,558 a c r e s i n F i s c a l Year 1979 ( 1 ) , but l a r g e r amounts were used i n the e a r l y 1970's when more funds were b e i n g a l l o c a t e d f o r i n t e n s i v e f o r e s t management.

0097-6156/85/0273-O109$06.00/0 © 1985 A m e r i c a n C h e m i c a l Society

Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

110

DERMAL EXPOSURE RELATED TO PESTICIDE USE

Several m i l l i o n acres o f young, overstocked stands a r e a t o r near t h e age where precommercial t h i n n i n g i s needed. MSMA i n p a r t i c u l a r , and p o s s i b l y c a c o d y l i c a c i d , c o u l d be i m p o r t a n t t o o l s f o r t h i s p u r p o s e , but both b e n e f i t s and r i s k s must be a s s e s s e d . P a r t i c u l a r l y a t r i s k a r e p e s t i c i d e a p p l i c a t o r s , who have t h e g r e a t e s t , and o n l y s u b s t a n t i v e , p o t e n t i a l f o r e x p o s u r e . The p u r p o s e o f t h i s paper i s (1) t o review ( a ) s t u d i e s o f a p p l i c a t o r exposure to MSMA and c a c o d y l i c a c i d and (b) s t r a t e g i e s f o r a p p l i c a t o r p r o t e c t i o n and (2) t o c a l c u l a t e magnitude o f a p p l i c a t o r e x p o s u r e .


A p p l i c a t i o n Methods and O p p o r t u n i t i e s

f o r Exposure

MSMA and c a c o d y l i c a c i d a r e i n j e c t e d i n t o t h e t r e e cambium by one o f t h r e e methods: . Hack and s q u i r t — a x e o r h a t c h e t used t o c u t i n t o t h e stem, u s u a l l y one c u t p e r i n c h o f d i a m e t e r , and h e r b i c i d e a p p l i e d w i t h a p l a s t i c squeeze b o t t l e o r pump-type o i l c a n , . I n j e c t i o n h a t c h e t — s p e c i a l l y d e s i g n e d h a t c h e t c o n t a i n i n g an i n e r t i a - d r i v e n p i s t o n which f o r c e s the h e r b i c i d e c o n c e n t r a t e i n t o t h e c u t when t h e h a t c h e t s t r i k e s t h e t r e e stem, and . I n j e c t i o n b a r — l o n g tube ( c o n t a i n i n g h e r b i c i d e ) w i t h a narrow b i t on t h e e n d ; t h e b i t i s p l u n g e d i n t o t h e cambium a t t h e base o f t h e t r e e , and a small amount o f h e r b i c i d e e n t e r s t h e c u t i n t h e t r e e through a h o l e i n t h e b i t when t h e o p e r a t o r opens t h e val v e . Each method a l l o w s o p p o r t u n i t y f o r a p p l i c a t o r exposure a t t h r e e points: . T r a n s p o r t i n g and t r a n s f e r r i n g t h e h e r b i c i d e c o n c e n t r a t e from t h e m a n u f a c t u r e r ' s c o n t a i n e r to t h e a p p l i c a t i o n equipment, . C a r r y i n g , u s i n g , and r e p a i r i n g t h e a p p l i c a t i o n equipment i n t h e f i e l d , and . Emptying and c l e a n i n g a p p l i c a t i o n equipment a t the end o f t h e work d a y . Potential

Exposure

Indexes

A r s e n i c (As) has been r e p o r t e d i n a v a r i e t y o f t i s s u e s , any o f which a r e p o t e n t i a l l y u s e f u l as i n d e x e s to e x p o s u r e . However, t h e o r g a n i c p e n t a v a l e n t a r s e n i c a l s a r e not accumulated i n t i s s u e s and a r e rapidly excreted i n urine (2-4). Therefore, urine generally i s a p a r t i c u l a r l y v a l u a b l e index to a p p l i c a t o r e x p o s u r e . Exon e t a l . (J>) r e p o r t e d both u r i n e and f e c e s were i m p o r t a n t pathways o f e x c r e t i o n i n r a b b i t s exposed to MSMA i n t h e i r f e e d . They found 70% o f i n g e s t e d As had been e x c r e t e d (54% i n u r i n e , 46% i n f e c e s ) d u r i n g a 17-week exposure p e r i o d . A r s e n i c l e v e l s i n l i v e r , h a i r , and u r i n e were t h e same as i n c o n t r o l s a f t e r 12 weeks o f MSMA exposure f o l l o w e d by 5 weeks o f c o n t r o l r a t i o n s , i n d i c a t i n g e x c r e t i o n was u l t i m a t e l y f a i r l y complete. H a i r and b l o o d a r e p o s s i b l e i n d e x e s o f a p p l i c a t o r e x p o s u r e . Exon e t a l . (5) r e p o r t e d As a c c u m u l a t i o n i n h a i r o f r a b b i t s , but about 4 weeks o f c o n t i n u o u s exposure t o MSMA i n t h e i r f e e d were r e q u i r e d b e f o r e t h e c o n c e n t r a t i o n was h i g h enough to measure w i t h confidence. D i c k i n s o n (J5) r e p o r t e d n o n s i g n i f i c a n t As a c c u m u l a t i o n



8.

NORRIS

MSMA

and Cacodylic

Acid

Exposure

in

Forestry

111

i n h a i r o f c a t t l e f e d enough MSMA i n t h e i r d i e t (10 mg/kg/day f o r 10 o r 12 days) to cause the death o f the a n i m a l s . However, As c o n c e n t r a t i o n i n c r e a s e d measurably i n 10 days i n h a i r o f c a t t l e exposed t o 10 mg/kg/day o f c a c o d y l i c a c i d ; t h e c o n c e n t r a t i o n c o n t i n u e d to i n c r e a s e w i t h d u r a t i o n o f e x p o s u r e . Arsenic in hair may be a u s e f u l index to l o n g - t e r m As e x p o s u r e , but i t does not respond w i t h s u f f i c i e n t speed to be u s e f u l i n s h o r t - t e r m t e s t s o r f o r operational monitoring of workers. Wagner and Weswig il) found a s l i g h t i n c r e a s e i n As l e v e l s i n b l o o d o f f o r e s t workers a p p l y i n g c a c o d y l i c a c i d , but t h e i n c r e a s e s were q u i t e e r r a t i c and were not a p p a r e n t b e f o r e t h e second week o f e x p o s u r e . H a i r i s simple to c o l l e c t and a n a l y z e , but a r s e n i c l e v e l s i n h a i r do not respond r a p i d l y to e x p o s u r e . B l o o d both i s d i f f i c u l t t o c o l l e c t and does not g i v e a c o n s i s t e n t o r r a p i d enough response t o As exposure o f an o r g a n i s m . T h u s , even w i t h t h e a t t e n d a n t c o l l e c t i o n p r o b l e m s , u r i n e i s t h e most p r a c t i c a l index t o the exposure o f f o r e s t workers to t h e o r g a n i c a r s e n i c a l h e r b i c i d e s . U n f o r t u n a t e l y , t h e p h a r m a c o k i n e t i c s o f these h e r b i c i d e s have not been f u l l y developed f o r dermal e x p o s u r e , and t h e r e a r e i n d i c a t i o n s t h a t u r i n e i s not t h e s o l e e x c r e t o r y r o u t e . Thus, estimates of exposure based o n l y on As e x c r e t i o n i n u r i n e may be o n l y 30% o f a c t u a l exposure l e v e l s (j>, 8 ) . Applicator

Exposure and I n f l u e n c e o f P r o t e c t i v e

Strategies

The F i r s t S t u d y . F o r e s t - a p p l i c a t o r exposure to MSMA and c a c o d y l i c a c i d was f i r s t s t u d i e d by T a r r a n t and A l l a r d ( 9 ) . They c o l l e c t e d i n d i v i d u a l u r i n e samples on Monday mornings ariïï F r i d a y a f t e r n o o n s f o r 9 c o n s e c u t i v e weeks from f i v e a p p l i c a t o r s (each u s i n g a d i f f e r e n t c o m b i n a t i o n o f a p p l i c a t i o n method and c h e m i c a l ) and one control. Workers were s u p p l i e d w i t h c l e a n c l o t h e s d a i l y , i n c l u d i n g two p a i r o f c o t t o n g l o v e s ( t o be changed a t noon, o r e a r l i e r i f one p a i r became s u b s t a n t i a l l y c o n t a m i n a t e d w i t h h e r b i c i d e ) . Complete data were o b t a i n e d f o r weeks 2, 3, 4 , 7, and 8 ( e x c e p t f o r t h e i n j e c t i o n h a t c h e t - c a c o d y l i c a c i d c o m b i n a t i o n , w h i c h was not i n c l u d e d i n the a n a l y s i s ) . A n a l y s i s o f v a r i a n c e showed t h a t As c o n c e n t r a t i o n i n u r i n e was s i g n i f i c a n t l y h i g h e r (P < 0 . 0 5 ) t h a n i n t h e c o n t r o l ( T a b l e I ) . C o n c e n t r a t i o n was h i g h e r by t h e end o f t h e f i r s t work week, and F r i d a y l e v e l s were h i g h e r t h a n t h e s u c c e e d i n g Monday l e v e l s , i n d i c a t i n g absence from c o n t a c t o v e r the weekend was s u f f i c i e n t t o complete e l i m i n a t i o n ( e x c e p t i n a few c a s e s where F r i d a y l e v e l s were s u b s t a n t i a l l y h i g h e r than a v e r a g e ) . The F r i d a y c o n c e n t r a t i o n s d i d not i n c r e a s e s u b s t a n t i v e l y o v e r t h e 9 weeks, which a l s o i n d i c a t e s r a p i d c l e a r a n c e and l a c k o f a c c u m u l a t i o n . None o f the workers e x p e r i e n c e d i l l n e s s t h a t seemed a s s o c i a t e d w i t h the h e r b i c i d e exposure. O f f i c i a l s t a n d a r d s f o r As i n u r i n e f o l l o w i n g exposure t o t h e s e compounds i s l a c k i n g , o t h e r than one m a n u f a c t u r e r ' s recommendation o f 0 . 3 ppm. T h i s s t a n d a r d appears t o be based on a study o f u r i n a r y e x c r e t i o n o f a r s e n i c i n 163 unexposed i n d i v i d u a l s , which showed a maximum e x c r e t i o n v a l u e o f 0 . 8 5 mg As/day ( 1 0 ) ; t h e 0 . 3 ppm c o n c e n t r a t i o n was s e l e c t e d based on a 3 - l i t e r d a i l y v o i d o f u r i n e and i s t h e r e f o r e q u i t e c o n s e r v a t i v e . In the T a r r a n t and A l l a r d



112

study (9), 47% o f t h e F r i d a y v a l u e s were > 0 . 3 ppm; t h e maximum v a l u e was 2 . 5 ppm. In c o n t r a s t , o n l y 4% o f t h e o b s e r v a t i o n s ( a l l i n t h e i n j e c t i o n h a t c h e t - c a c o d y l i c a c i d t r e a t m e n t group) were > 0 . 3 ppm on Mondays.

Table I. Mean C o n c e n t r a t i o n {±1 S t a n d a r d D e v i a t i o n ) o f A r s e n i c i n U r i n e from F o r e s t Workers a t 2, 3, 4 , 7, and 8 Weeks o f a 9-Week Exposure P e r i o d [9)


Total A p p l i c a t i o n Method and Chemical

As(mg/1) Friday

Monday

% >

% >

0 . 3 ppm

0 . 3 ppm Control, no exposure Hack and s q u i r t , MSMA Hack and s q u i r t , cacodylic acid Injection hatchet, MSMA Injection bar, MSMA

0.04

( i 0.01)

0

0.07

( + 0.03)

4

0.07

( 1 0.01)

0

0.26

( + 0.05)

32

0.03

i*

0.01)

0

0.41

( 1 0.08)

46

0.10

( + 0.01)

0

0.50

(1 0.12)

54

0.10

( 1 0.01)

0

0.36

0.07)

42

S o u r c e : Reproduced w i t h p e r m i s s i o n from R e f . 9 . American M e d i c a l A s s o c i a t i o n .

C o p y r i g h t 1972,

Follow-up S t u d i e s . The r e s u l t s o f t h e T a r r a n t and A l l a r d study ( 9 ) , combined w i t h an i n c i d e n t i n which s e v e r a l dead snowshoe hares w i t h e l e v a t e d l e v e l s o f As (more than 100 ppm i n v a r i o u s t i s s u e s ) were found i n a t r e a t e d a r e a , prompted an i n t e n s i v e e f f o r t t o f u r t h e r e l u c i d a t e p a t t e r n s o f a p p l i c a t o r exposure and t o e v a l u a t e means o f r e d u c i n g exposure to humans and o t h e r a n i m a l s . I n v e s t i g a t i o n o f t h e hare m o r t a l i t y i n c i d e n t r e v e a l e d t h a t c a r e l e s s h a n d l i n g t e c h n i q u e s and poor p r o c e d u r e s f o r d i s p o s i n g o f l e f t o v e r h e r b i c i d e and c l e a n - u p w a t e r were t h e l i k e l y s o u r c e s o f As f o r t h e hares ( t h e h i g h s a l t c o n t e n t o f t h e m a t e r i a l p r o b a b l y a t t r a c t e d them). In i n t e r v i e w s , w o r k e r s from t h e T a r r a n t and A l l a r d study i n d i c a t e d t h a t t h e i r c o t t o n g l o v e s i n p a r t i c u l a r and sometimes p o r t i o n s o f t h e i r c l o t h i n g became q u i t e wet w i t h h e r b i c i d e . In a d d i t i o n , t h e i r hands c o n t a c t e d t h e h e r b i c i d e when t h e a p p l i c a t i o n equipment was b e i n g f i l l e d w i t h h e r b i c i d e c o n c e n t r a t e o r when t h e a p p l i c a t i o n equipment had t o be r e p a i r e d o r c l e a n e d . In some c a s e s workers were " s p l a s h e d " w i t h t h e h e r b i c i d e d u r i n g a c t u a l a p p l i c a t i o n . A l l a r d (11) c o n d u c t e d a second round o f t e s t s t o determine how As l e v e l s i n u r i n e c o u l d be reduced through worker t r a i n i n g and improved p r o t e c t i o n . In t h i s t e s t , a p p l i c a t o r s wore g o g g l e s , used an i m p e r v i o u s f a c e c r e a m , and were i n s t r u c t e d i n b e t t e r t e c h n i q u e s f o r h a n d l i n g o f both h e r b i c i d e c o n c e n t r a t e and a p p l i c a t i o n equipment. In a d d i t i o n , two groups used rubber g l o v e s i n s t e a d o f cotton gloves.


8.

MSMA

NORRIS

and Cacodylic

Acid

Exposure

in

113

Forestry


A r s e n i c l e v e l s i n u r i n e were s u b s t a n t i a l l y reduced i n a l l crews but t h e K a n i k s u ( T a b l e I I ) . I t was c o n c l u d e d from p e r i o d i c o b s e r v a t i o n s and i n t e r v i e w s o f crew members and foremen t h a t i m p e r v i o u s g l o v e s , s k i n cream, and e f f e c t i v e t r a i n i n g and s u p e r v i s i o n were t h e kçy f a c t o r s . The foreman and the t r a i n e r o f t h e C o l v i l l e crew had been p a r t i c u l a r l y e f f e c t i v e ; As l e v e l i n u r i n e f o r t h a t c r e w , w h i c h wore o n l y c o t t o n g l o v e s , was s i m i l a r to t h a t o f one crew wearing r u b b e r g l o v e s , and t h e number o f o b s e r v a t i o n s > 0 . 3 ppm was o n l y 1/3 t h a t o f a s i m i l a r crew i n the same area t h e previous year (Table I ) .

Table I I . Mean C o n c e n t r a t i o n o f A r s e n i c i n U r i n e from F o r e s t Workers A p p l y i n g MSMA o r C a c o d y l i c A c i d v i a t h e Hack and S q u i r t Method i n O p e r a t i o n a l Precommercial T r e e T h i n n i n g ill)

Total

il As (ppm)

J

Monday

Frioây"

>

% > 0 . 3 ppm

Crew

Mean

Max.

0 . 3 ppm

Mean

Max.

MSMA Colville Okanogan Wenatchee Cedar Creek Naselle

0.05 0.07 0.03 0.04 0.04

0.37 0.50 0.14 0.09 0.20

8 9 0 0 0

0.15 0.24 0.07 0.02 0.14

0.46 1.30 0.35 0.03 0.54

11 33 7 0 14

Cacodylic Kaniksu

0.01

0.02

0

0.80

1.80

75

2

1 2

Acid

C o n t r o l s averaged 0 . 0 2 ppm. Crews used r u b b e r g l o v e s i n s t e a d o f c o t t o n

gloves.

Wagner and Weswig (7) implemented the b e s t o f a l l t h e s e p r o c e d u r e s i n m o n i t o r i n g an o p e r a t i o n a l t h i n n i n g program a y e a r later. The crew c o n s i s t e d o f f i v e c o l l e g e s t u d e n t s and a f u l l - t i m e s u p e r v i s o r who were c a r e f u l l y t r a i n e d i n p r o p e r p r o c e d u r e s f o r h a n d l i n g t h e h e r b i c i d e ( c a c o d y l i c a c i d ) and t h e hack and s q u i r t method. A l l were impressed w i t h t h e importance o f m i n i m i z i n g p e r s o n a l exposure and based on t h e i r p e r f o r m a n c e , seemed t o have approached t h e study as something o f a p e r s o n a l c r u s a d e . Wagner and Weswig c o l l e c t e d 24-hour u r i n e samples from each worker b e g i n n i n g l a t e Thursday a f t e r n o o n and c o n t i n u i n g u n t i l the end o f t h e work day on F r i d a y , when b l o o d samples were c o l l e c t e d and analyzed (Table I I I ) . A t no time d u r i n g t h e exposure p e r i o d o f 7 weeks (5 work days/week) d i d As c o n c e n t r a t i o n i n u r i n e exceed 0 . 2 ppm. A r s e n i c e x c r e t i o n i n c r e a s e d once exposure began, r e a c h i n g t h e average l e v e l d u r i n g t h e second week o f e x p o s u r e , but f e l l r a p i d l y when exposure ended, r e i n f o r c i n g t h e r e s u l t s from the animal


114


T a b l e I I I . Mean C o n c e n t r a t i o n i n B l o o d and E x c r e t i o n i n U r i n e o f A r s e n i c from F i v e F o r e s t Workers Exposed t o C a c o d y l i c A c i d and F i v e C o n t r o l s (2) Workers Week

1

Exposed

Control s


Arsenic

i n b l o o d (ppm)

1 2 3 4 5 6 7 8 9 10

0.05 0.17 0.26 0.19 0.06 0.06 0.03 0.03 0.04 0.01

0.05

11

0.02

0.02

1 2 3 4 5 6 7 8 9 10 11

0.038 0.077 0.141 0.172 0.106 0.103 0.169 0.204 0.024 0.068 —

0.06

Arsenic

in urine

(mg/24 h) 0.073

0.042

0.026

Week 1 was a p r e - e x p o s u r e p e r i o d ; weeks 2 t h r o u g h 8 were f u l l 5-day work weeks, a l t h o u g h work r e c o r d s i n d i c a t e a p p l i c a t i o n accounted f o r o n l y 2 3 . 7 hours o f each 40-hour work week, and each worker a p p l i e d an average o f 817 g d i m e t h y l a r s i n i c a c i d / w e e k ; week 9 i n c l u d e d o n l y 10 hours o f e x p o s u r e , which o c c u r r e d d u r i n g t h e f i r s t 2 days o f t h e week; weeks 10 and 11 were p o s t - e x p o s u r e periods. 1

Source: Reproduced w i t h p e r m i s s i o n from R e f . 7. American M e d i c a l A s s o c i a t i o n .

C o p y r i g h t 1974,


8.

NORRIS

MSMA

and Cacodylic

Acid

Exposure

in

115

Forestry

f e e d i n g s t u d i e s [5). Though As l e v e l i n b l o o d i n i t i a l l y i n c r e a s e d , i t d e c r e a s e d t o c o n t r o l l e v e l s i n 4 weeks and c o r r e l a t e d p o o r l y ( c o r r e l a t i o n c o e f f i c i e n t = 0 . 1 4 ) w i t h As e x c r e t i o n i n u r i n e . On t h e b a s i s o f 70 kg body w e i g h t and the assumptions t h a t (1) e x c r e t i o n l e v e l measured a t t h e end o f the week i s r e p r e s e n t a t i v e o f t h e d a i l y r a t e and (2) u r i n e i s the p r i n c i p a l r o u t e o f e x c r e t i o n , t h e s e workers were exposed t o an a v e r a g e o f 0 . 0 0 2 mg As/kg body w e i g h t / d a y .


Monitoring Operational

Projects

Seven o p e r a t i o n a l a p p l i c a t i o n u n i t s were m o n i t o r e d on the b a s i s o f i n f o r m a t i o n from t h e p r e v i o u s t e s t s i n an e f f o r t t o m i n i m i z e a p p l i c a t o r e x p o s u r e (JL1). Operational monitoring involved six i n d i v i d u a l a p p l i c a t i o n crews o f from f i v e to ten a p p l i c a t o r s ; one crew t r e a t e d two u n i t s . A l l crews used t h e hack and s q u i r t method, but some a p p l i e d c a c o d y l i c a c i d and o t h e r s MSMA. The time r e q u i r e d to complete a u n i t v a r i e d from 1 t o 3 months, but not a l l crews were i n v o l v e d w i t h c h e m i c a l t h i n n i n g each day. Each crew and foreman were b r i e f e d on r e s u l t s o f p r e v i o u s s t u d i e s , and t h e importance o f m i n i m i z i n g p e r s o n a l exposure was emphasized. G u i d e l i n e s on a p p l i c a t i o n equipment, p r o t e c t i v e g e a r , and methods o f h a n d l i n g and a p p l y i n g the h e r b i c i d e t o m i n i m i z e e x p o s u r e were p r e s e n t e d . Type and d e n s i t y o f v e g e t a t i o n , roughness o f t e r r a i n , and c l i m a t i c f a c t o r s v a r i e d such t h a t the method and p r o t e c t i v e equipment b e s t s u i t e d to each c i r c u m s t a n c e were implemented; no e f f o r t to " s t a n d a r d i z e " was made, e m p h a s i z i n g t h e o p e r a t i o n a l n a t u r e o f the t e s t s . S i n g l e u r i n e samples were c o l l e c t e d from each a p p l i c a t o r i n each u n i t near the end o f the work day on F r i d a y ; a s i m i l a r sample was c o l l e c t e d e v e r y t h i r d Monday, b e f o r e the work day began. Of the seven u n i t s m o n i t o r e d , f i v e were h i g h l y s u c c e s s f u l (no As l e v e l s > 0 . 3 ppm), one was f a i r l y s u c c e s s f u l , and one ( K a n i k s u 1) was a f a i l u r e ( T a b l e I V ) .

T a b l e IY. Mean C o n c e n t r a t i o n o f A r s e n i c i n U r i n e from F o r e s t Workers i n Seven A p p l i c a t i o n U n i t s T h i n n e d w i t h MSMA o r C a c o d y l i c A c i d by t h e Hack and S q u i r t Method (12)

Total

As (ppm) Friday

Monday

%

%>

Application Unit Colville 1 Colville 2 Colville 3 Siuslaw 1 Naselle 1 Cedar Creek 1 Kaniksu 1

Mean

0.06 0.04 0.03 0.03 0.03 0.06 0.26

Max.

0.21 0.21 0.11 0.05 0.08 0.13 0.50

0 . 3 ppm

0 0 0 0 0 0 33

Mean

0.10 0.06 0.05 0.09 0.09 0.08 0.38

Max.

>

0 . 3 ppm

0.34 0.32 0.13 0.19 0.49 0.52 1.74


4 2 0 0 5 10 45


116


The p a t t e r n o f a r s e n i c i n u r i n e from t h e K a n i k s u 1 crew i s q u i t e i n t e r e s t i n g ( T a b l e Y ) . Mean As c o n c e n t r a t i o n i n c r e a s e d i m m e d i a t e l y , t h e number o f o b s e r v a t i o n s > 0 . 3 ppm e x c e e d i n g 50%. As soon as t h e s e r e s u l t s were a v a i l a b l e , t h e crew foreman and s u p e r v i s o r were n o t i f i e d , and they i n t e n s i f i e d e f f o r t s to reduce e x p o s u r e . They were p a r t i a l l y s u c c e s s f u l f o r about 2 weeks (17% o f o b s e r v a t i o n s > 0 . 3 ppm); then t h e a v e r a g e and maximum c o n c e n t r a t i o n s began t o rise. L a t e i n J u l y , 83% were > 0 . 3 ppm, and t h i n n i n g was stopped t o prevent f u t h e r a p p l i c a t o r exposure. D u r i n g t h e next 3 weeks, As c o n c e n t r a t i o n i n urine dropped. A f t e r 2 s u c c e e d i n g weeks when t h e a v e r a g e and maximum c o n c e n t r a t i o n s were i n t h e normal range ( 0 . 0 2 t o 0 . 0 3 ppm), t h e crew r e t u r n e d t o t h i n n i n g f o r 5 d a y s . All urine samples c o l l e c t e d a t t h e end o f t h a t p e r i o d exceeded 0 . 0 3 ppm A s ; they averaged 0 . 8 5 ppm, and maximum was 1.74 ppm!

Table Y.

Mean C o n c e n t r a t i o n o f A r s e n i c i n U r i n e A p p l i c a t i o n Crew U £ ) Total

Date

As (ppm)

~~ Crew Size

from K a n i k s u 1

"~ % > 0 . 3 ppm

Day

Mean

Range

Tue. Fri. Fri.

0.08 0.31 0.20

0.02-0.20 0.08-0.42 0.04-0.33

5 5 5

0 60 20

Fri. Tue. Fri. Fri. Fri. Mon. Fri.

0.21 0.17 0.15 0.29 0.72 0.53 0.49

0.05-0.33 0.03-0.48 0.07-0.37 0.05-0.68 0.19-1.32 0.11-1.01 0.10-1.38

6 6 6 6 6 6 6

33 17 17 33 67 83 50

6 6 5

17 0 0

3

100

June 18 25 July

—r 6 9 16 23 26 30 August 2 6 13 20 23 27

Chemical t h i n n i n g suspended 0.13-0.36 0.17 Fri. 0.02-0.03 Fri. 0.02 0.01-0.03 0.02 Fri. T h i n n i n g resumed 0.32-1.74 0.85 Fri. ( L a s t day o f t h i n n i n g )

The d a i l y d i a r y o f t h e K a n i k s u 1 foreman noted numerous o c c a s i o n s when a p p l i c a t o r s r e c e i v e d c o n s i d e r a b l e exposure as a r e s u l t o f p o o r h a n d l i n g p r a c t i c e s and use o f i n a p p r o p r i a t e g e a r . C o i n c i d e n t w i t h a p p l i c a t o r m o n i t o r i n g , however, small mammals ( u s u a l l y mice) were t r a p p e d i n t h e s e seven u n i t s and a n a l y z e d f o r arsenic. I n t e r e s t i n g l y (though t h e d e t a i l s a r e beyond t h e scope o f


8.

MSMA

NORRIS

and Cacodylic

Acid

Exposure

in

117

Forestry

t h i s p a p e r ) , t h e r e was a s t r o n g r e l a t i o n s h i p between As c o n c e n t r a t i o n i n small mammals and t h a t i n a p p l i c a t o r u r i n e ( T a b l e Y D — w h i c h l e a d s me to b e l i e v e t h a t c a r e i n a p p l i c a t i o n i s predominant f a c t o r i n f l u e n c i n g small animal as well as human exposure. T h u s , m o n i t o r i n g a p p l i c a t o r u r i n e f o r As may be u s e f u l an index to both a p p l i c a t o r and animal e x p o s u r e .


As C o n c e n t r a t i o n

i n U r i n e R e l a t e d to 24-Hour E x c r e t i o n

in

a as

Urine

Wagner and Weswig (7) recommended 24-hour As e x c r e t i o n i n u r i n e as the b e s t measure o f " a p p l i c a t o r e x p o s u r e . Though u s e f u l i n e x p e r i m e n t a l work, t h i s measure i s i m p r a c t i c a l as an o p e r a t i o n a l m o n i t o r i n g t o o l : t h e l i k e l i h o o d o f workers s u c c e s s f u l l y c o l l e c t i n g uncontaminated 24-hour u r i n e samples on a r o u t i n e b a s i s seems l o w . The b e s t m o n i t o r i n g t o o l i s t h e one which " w i l l be used" and which g i v e s a r e a s o n a b l y good index to e x p o s u r e .

Table YI.

Arsenic

Mean C o n c e n t r a t i o n o f A r s e n i c i n Whole B o d i e s o f Mammals and i n U r i n e from A p p l i c a t o r s (12)

in A p p l i c a t o r Urine

Application Units

7o F r i d a y Observations > 0 . 0 3 ppm

Colville 1 Colville 2 Colville 3 S i l l si aw 1 Kaniksu 1

4 2 0 0 45

1

No d a t a f o r N a s e l l e

Arsenic

i n Small-Mammal

% < 0.5 ppm 54 72 38 83 20

o r Cedar Creek

> 1 ppm 9 9 37 0 50

Small

Whole B o d i e s

Observations > 3 ppm Ζ 0 9 0 25

> 5 ppm 0 0 0 0 15

units.

N o r r i s (13) c o n d u c t e d a stutty to determine the r e l a t i o n s h i p , i f any, b e t w e e n T s c o n c e n t r a t i o n i n a s i n g l e ( s m a l l ) u r i n e sample and As e x c r e t i o n i n u r i n e o v e r a 24-hour p e r i o d . In t h i s s t u d y , 17 workers a p p l i e d MSMA by t h e hack and s q u i r t method. On t h e d e s i g n a t e d c o l l e c t i o n day, each crew member r e c e i v e d one l a r g e and one small c o n t a i n e r ; a l l u r i n e e x c r e t e d d u r i n g t h e 24-hour p e r i o d was c o l l e c t e d i n t h e l a r g e c o n t a i n e r e x c e p t t h a t e x c r e t e d a t the end o f t h e work day, which was c o l l e c t e d i n the small c o n t a i n e r . The p a i r e d samples (one l a r g e and one s m a l l ) c o n s t i t u t e d a sample s e t . The number o f sample s e t s from any one i n d i v i d u a l ranged from one t o n i n e (average 3 . 3 ) ; i n t o t a l , 56 sample s e t s were c o l l e c t e d . The volume o f both samples i n a s e t was measured and u r i n e a n a l y z e d f o r t o t a l A s , c r e a t i n i n e , and o s m o l a l i t y . M u l t i p l e r e g r e s s i o n a n a l y s i s o f d a t a showed t h a t the independent v a r i a b l e s ( u r i n e volume, As c o n c e n t r a t i o n , mg% c r e a t i n i n e , and o s m o l a l i t y ) accounted f o r 76% o f t h e v a r i a t i o n i n the dependent v a r i a b l e (ug As e x c r e t e d i n 24 h o u r s ) . Adding independent v a r i a b l e s



118

s t e p w i s e , i n o r d e r o f t h e i r i m p o r t a n c e , showed t h a t : . A r s e n i c c o n c e n t r a t i o n i n t h e small sample a c c o u n t e d f o r 73.4% of the v a r i a t i o n , . U r i n e volume and As c o n c e n t r a t i o n i n t h e small sample a c c o u n t e d f o r 75.9% o f t h e v a r i a t i o n , and . The o t h e r i n d e p e n d e n t v a r i a b l e s d i d not s i g n i f i c a n t l y improve t h e model· T h u s , two t y p e s o f d a t a , e a s i l y c o l l e c t e d , c o u l d be used to p r e d i c t a p p l i c a t o r exposure w i t h r e a s o n a b l e a c c u r a c y i n o p e r a t i o n a l m o n i t o r i n g programs, a c c o r d i n g t o t h e r e l a t i o n s h i p : Y = 12.88 + 1386 (Χχ) + 0 . 1 4 ( X ) ; r = 0 . 7 6 where: Y = ug As e x c r e t e d i n 24 h o u r s , X l = ppm As i n a s i n g l e u r i n e sample c o l l e c t e d a t t h e end o f t h e work day, and X2 = ml u r i n e i n t h e sample. 2


2

In t h i s s t u d y , t h e average As c o n c e n t r a t i o n was 0.075 ppm (maximum 0 . 2 8 ppm), and t h e a v e r a g e amount o f As e x c r e t e d 126 ug/24 hours (maximum 323 ug/24 h o u r s ) . On t h e b a s i s o f 70 kg body w e i g h t , t h e s e workers were exposed to an average o f 0.002 (maximum o f 0.005) mg As/kg body w e i g h t / d a y . S i m i l a r v a l u e s were r e p o r t e d by Wagner and Weswig (7). Calculating Applicator

Exposure

With t h e p o s s i b l e e x c e p t i o n o f Wagner and Weswig (7) and N o r r i s ( 1 3 ) , none o f t h e s t u d i e s on a p p l i c a t o r exposure gTves more than an iïï3ex to e x p o s u r e , based on r i s i n g and f a l l i n g As c o n c e n t r a t i o n i n s i n g l e u r i n e samples. U n f o r t u n a t e l y ( f o r t h i s p u r p o s e ) , both Wagner and Weswig (2) and N o r r i s ( j ^ ) examined s i t u a t i o n s where a p p l i c a t o r exposure was q u i t e l o w . However, exposure can be c a l c u l a t e d u s i n g the s e v e r a l o t h e r d a t a s e t s i n t h i s paper and t h e f o l l o w i n g assumptions: . A l l a r s e n i c absorbed i s e x c r e t e d i n u r i n e — T h e v a l i d i t y o f t h i s assumption needs t e s t i n g ; f o r i n s t a n c e , p o s s i b l e As e x c r e t i o n i n p e r s p i r a t i o n has not been a d d r e s s e d . If this assumption i s not v a l i d , c a l c u l a t e d exposure l e v e l s w i l l be two to t h r e e times l o w e r than a c t u a l ( 5 , 8 ) . . mg As e x c r e t e d / d a y = 12.88 + 13"56(ppm As i n s i n g l e urirte sample) + 0.14(ml u r i n e i n s i n g l e s a m p l e ) — T h e v a l i d i t y o f t h i s assumption depends on t h e degree t o which t h e N o r r i s U 3 ) r e l a t i o n s h i p i s accurate a t higher l e v e l s of arsenic exposure. . The average volume o f u r i n e v o i d e d i n a s i n g l e sample i s 373 m l — b a s e d on t h e average r e p o r t e d by N o r r i s [13). . The botty w e i g h t o f t h e average f o r e s t worker i s 70 k g . U s i n g t h e d a t a i n T a b l e s I - I V and these a s s u m p t i o n s , I have c a l c u l a t e d t h e mean and maximum a p p l i c a t o r exposure f o r each d a t a s e t i n t h i s paper ( T a b l e V I I ) . The o v e r a l l average was 0.005 mg As/kg body w e i g h t / d a y , t h e h i g h e s t i n d i v i d u a l maximum 0 . 0 3 6 mg As/kg body w e i g h t / d a y . I f u r i n e i s not t h e s o l e e x c r e t o r y s o u r c e o f A s , t h e o v e r a l l average c o u l d be 0 . 0 1 5 mg As/kg botty weight/day and t h e h i g h e s t i n d i v i d u a l maximum 0 . 0 1 8 mg As/kg body w e i g h t / d a y .


8.

NORRIS

Table V I I .

MSMA

and Cacodylic Acid Exposure in Forestry

Exposure o f F o r e s t Workers t o MSMA o r C a c o d y l i c Summary o f Data S e t s P r e s e n t e d i n P r i o r T a b l e s Total in Urine,


Crew

2

Table I A Β C D T a b l e II Ε F G H I J T a b l e IV K L M N 0 Ρ Q

119

C a l c u l a t e d As

As

Acid:

Exposure

(ppm)

(mg/kg/day)

% > 0 . 3 ppm

Mean

Max.

Friday

1

Mean

Max.

0.26 0.41 0.50 0.36

0.36 0.51 0.93 0.58

32 46 54 42

0.006 0.009 0.011 0.008

0.008 0.011 0.019 0.012

0.15 0.24 0.07 0.02 0.14 0.80

0.46 1.30 0.35 0.03 0.54 1.80

11 33 7 0 14 75

0.004 0.006 0.002 0.001 0.004 0.017

0.010 0.027 0.008 0.001 0.012 0.036

0.10 0.06 0.05 0.09 0.09 0.08 0.38

0.34 0.32 0.13 0.19 0.49 0.52 1.74

4 2 0 0 5 10 45 Average Maximum

0.003 0.002 0.002 0.003 0.003 0.003 0.008 O 0 5 0.017

0.008 0.007 0.004 0.005 0.011 0.011 0.035 0.013 0.036

Based on t h e f o u r assumptions proposed i n the t e x t : (a) a l l a r s e n i c e x c r e t e d i n u r i n e ; (b) mg As e x c r e t e d / d a y = 1 2 . 8 8 + 1 3 8 6 (ppm As i n u r i n e ) + 0 . 1 4 (ml u r i n e e x c r e t e d i n one s a m p l e ) , see J 3 ^ 3 7 3 ml u r i n e e x c r e t e d i n one sample, see j _ 3 ; (d) 70 kg body w e i g h t . Upper c a s e l e t t e r s r e p r e s e n t e n t r i e s , i n o r d e r , from T a b l e s I - I V . U p p e r case l e t t e r s r e p r e s e n t from T a b l e s I , I I , and I V . 2

entries

for

exposed w o r k e r s ,

in


order,


120


Conclusions The c o n c e n t r a t i o n o f t o t a l a r s e n i c i n u r i n e i n c r e a s e s and d e c r e a s e s r a p i d l y w i t h I n i t i a t i o n and t e r m i n a t i o n o f a p p l i c a t o r e x p o s u r e ; l e v e l s i n u r i n e u s u a l l y a r e near normal by the Monday morning f o l l o w i n g a f u l l week o f chemical t h i n n i n g . M o r e o v e r , As l e v e l o f exposed a p p l i c a t o r s seems to p a r a l l e l t h a t i n small mammals in treated areas. The use o f i m p e r v i o u s g l o v e s , long-sleeved s h i r t s , and s i l i c o n f a c e c r e a m , combined w i t h e f f e c t i v e t r a i n i n g and s u p e r v i s i o n , markedly reduces u r i n e a r s e n i c l e v e l s . Thus, a u r i n e m o n i t o r i n g program can g i v e a good index to exposure o f humans and o t h e r animals d u r i n g o p e r a t i o n a l t h i n n i n g . Even s i n g l e u r i n e samples can be used to p r o j e c t d a i l y As e x c r e t i o n , f a c i l i t a t i n g m o n i t o r i n g and c a l c u l a t i o n o f a p p l i c a t o r e x p o s u r e . S e v e r a l m o n i t o r i n g e f f o r t s s u g g e s t t h a t f o r e s t workers a p p l y i n g MSMA and c a c o t t y l i c a d d may be exposed to As l e v e l s as h i g h as 0.036 mg/kg (average 0 . 0 0 5 m g / k g ) , a l t h o u g h the a c t u a l l e v e l varies w i t h the worker and the p r o t e c t i v e measures employed. However, t h e s e l e v e l s l i k e l y a r e u n d e r e s t i m a t e s because u r i n e may not be the o n l y source o f e x c r e t i o n . N o n t e c h n i c a l Summary MSMA and c a c o d y l i c a c i d h e r b i c i d e s a r e used to t h i n o v e r s t o c k e d f o r e s t stands. Although these a r s e n i c c o n t a i n i n g h e r b i c i d e s are i n j e c t e d i n t o the t r e e stem, a p p l i c a t o r s may s t i l l be exposed d u r i n g the h a n d l i n g , a p p l i c a t i o n and c l e a n - u p s t a g e s o f o p e r a t i o n . The amount o f a r s e n i c i n u r i n e i s a good i n d i c a t o r o f a p p l i c a t o r exposure. The f i r s t t e s t s conducted d u r i n g o p e r a t i o n a l t h i n n i n g programs showed t h e l e v e l s o f a p p l i c a t o r exposure were h i g h e r than a d v i s e d , and t h e r e appeared to be a c o r r e l a t i o n between the l e v e l s o f a r s e n i c i n u r i n e from a p p l i c a t o r s and the whole body l e v e l s o f a r s e n i c i n small a n i m a l s . T h i s suggests t h a t minimizing a p p l i c a t o r exposure w i l l a l s o reduce exposure to small mammals. Later tests showed e f f e c t i v e worker t r a i n i n g and s u p e r v i s i o n , and the use o f p r o t e c t i v e gear are e f f e c t i v e i n t h i s regard. Monitoring a r s e n i c i n a p p l i c a t o r u r i n e i s u s e f u l f o r d e t e r m i n i n g i f exposure g o a l s a r e b e i n g a c h i e v e d d u r i n g o p e r a t i o n a l f o r e s t t h i n n i n g w i t h MSMA and cacottylic a c i d h e r b i c i d e s . Acknowledgments T h i s r e s e a r c h i s s u p p o r t e d i n p a r t by USDA F o r e s t S e r v i c e , Northwest F o r e s t and Range E x p e r i m e n t S t a t i o n , PNW 84-359.

Pacific

Literature Cited 1. "Pesticide-use Advisory Memorandum 246,"USDAForest Service, 1980. 2. Schroeder, Η. Α.; Balassa, J. J. J. Chronic Dis. 1966, 19, 85-106. 3. Hogan, R. B.; Eagle, H. J. Pharmacol. Exp. Ther. 1944, 80, 93-113.



8.

NORRIS

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and

Cacodylic

Acid

Exposure

in

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4. Frost, D. V. Fed. Proc. Fed. Am. Soc. Exp. Biol. 1967, 26, 194-208. 5. Exon, J. H.; Harr, J. R.; Claeys, R. R. Nutr. Rep. Int. 1974, 9, 351-7. 6. Dickinson, J. O. Am. J. Vet. Res. 1972, 33, 1889-92. 7. Wagner, S. L.; Weswig, P. Arch. Environ. Health 1974, 28, 77-9. 8. Dutkiewicz, T. Environ. Health Persp. 1977, 19, 173-7. 9. Tarrant, R. F.; Allard, J. Arch. Environ. Health 1972; 24, 277-80. 10. Mattice, M. R.; Weisman, D. Amer. J. Med. Sci. 1937; 193, 413-20. 11. Allard, J., In "The Behavior and Impact of Organic Arsenical Herbicides in the Forest: Final Report of Cooperative Studies"; USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Portland, Oreg., 1974; pp. 4-8. 12. Norris, L. Α., In "The Behavior and Impact of Organic Arsenical Herbicides in the Forest: Final Report of Cooperative Studies"; USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Portland, Oreg., 1974; pp. 75-89. 13. Norris, L.A., In "The Behavior and Impact of Organic Arsenical Herbicides in the Forest: Final Report of Cooperative Studies"; USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Portland, Oreg., 1974; pp. 10-17. RECEIVED

December 3,1984


Exposure of Applicators to Monosodium Methanearsonate and

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